Electronic coordinated control for a two-axis work implement

Abstract

A loader of the type controlled with an electronic digital controller is disclosed herein. The loader may include conventional mechanical component. However, the hydraulic valve is electronically controlled to provide improved motion control. In particular, the operator controls the loader with a two-axis joystick. When the joystick is moved left or right, the bucket is rolled at a speed proportional to the rate of change of the joystick position and independent of the loader arms. When the joystick is moved forward or backwards, the loader arms of the bucket are raised or lowered. When the joystick is only moved forward or backward with substantially no component of motion left or right, the controller rolls the bucket to maintain a substantially constant angle between the bucket and the surface upon which the loader is operating.

What is claimed is: 
     
       1. A control for an implement of the type including at least one arm pivotally supported at a vehicle having a frame and an attachment pivotally attached to the arm, wherein the arm is pivoted relative to the vehicle by at least a first hydraulic actuator, and the attachment is pivoted relative to the arm by a second hydraulic actuator, the control comprising: a first position sensor supported to generate a first position signal representative of the position of the arm relative to the vehicle;   a second position sensor supported to generate a second position signal representative of the position of the attachment relative to the arm;   an input device including an operator interface assembly moveable by an operator relative to first and second axes, the device including a first signal generator for generating a first control signal representative of motion of the interface assembly about the first axis and a second signal generator for generating a second control signal representative of motion of the interface assembly about the second axis;   a hydraulic valve assembly responsive to a first valve signal to control hydraulic fluid flow to at least the first hydraulic actuator, and responsive to a second valve signal to control hydraulic fluid flow to the second hydraulic actuator; and   a digital control circuit coupled to the position sensors, the input device, and the hydraulic valve assembly to apply the first and second valve signals to the valve assembly such that hydraulic fluid flow is applied to at least the first hydraulic actuator to pivot the arm so that the first position signal and the first control signal maintain a first predetermined relationship, and hydraulic fluid flow is applied to the second hydraulic actuator to pivot the attachment so that the second position signal and the second control signal maintain a second predetermined relationship, wherein the second valve signal is generated independently of the second control signal when the interface assembly is only moved about the first axis such that the second hydraulic actuator pivots the attachment to maintain a third predetermined relationship between the attachment and the frame while the arm is pivoted by the first hydraulic actuator.   
     
     
       2. The control of claim 1, wherein the input device is a joystick, and the operator interface assembly is a lever. 
     
     
       3. The control of claim 2, wherein the first and second signal generators are first and second respective potentiometers coupled to the lever such that the first potentiometer is operated in response to motion of the lever about the first axis, and the second potentiometer is operated in response to motion of the lever about the second axis. 
     
     
       4. The control of claim 3, wherein the control circuit includes an analog-to-digital converter which converts the control signals generated by the potentiometers to digital control signals. 
     
     
       5. The control of claim 1, wherein the control circuit is configured such that the third predetermined relationship is a substantially constant angle between the attachment and the frame. 
     
     
       6. The control of claim 2, wherein the control circuit is configured such that the third predetermined relationship is a substantially constant angle between the attachment and the surface. 
     
     
       7. The control of claim 6, wherein the attachment is a bucket, and the hydraulic actuators are hydraulic cylinders. 
     
     
       8. The control of claim 2, wherein the hydraulic valve is a pulse-width-modulated (PWM) valve, and the control circuit is configured to generate first and second valve signals which are PWM signals. 
     
     
       9. The control of claim 2, wherein the control circuit is configured to apply the first and second valve signals to the valve assembly such that hydraulic fluid flow is applied to the first hydraulic actuator to pivot the arm so that the rate of change of the first position signal and the rate of change of the first control signal maintain a fourth predetermined relationship, and hydraulic fluid flow is applied to the second hydraulic actuator to pivot the attachment so that the rate of change of the second position signal and the rate of change of the second control signal maintain a fifth predetermined relationship. 
     
     
       10. The control of claim 9, wherein the control circuit is configured such that the first, second, fourth, and fifth predetermined relationships are proportional relationships. 
     
     
       11. The control of claim 10, wherein the fourth and fifth predetermined relationships are also integral relationships. 
     
     
       12. A loading system comprising: first and second arms pivotally supportable at a vehicle having a frame;   a bucket pivotally attached to the arms;   first and second hydraulic cylinders for pivoting the first and second arms, respectively, relative to the vehicle;   least a third hydraulic cylinder for pivoting the bucket relative to the arms;   at least a first position sensor supported to generate a first position signal representative of the position of the arms relative to the vehicle;   at least a second position sensor supported to generate a second position signal representative of the position of the bucket relative to the arms;   a joystick including a lever moveable by an operator about first and second axes, a first signal generator for generating a first control signal representative of motion of the lever about the first axis, and a second signal generator for generating a second control signal representative of motion of the lever about the second axis;   a hydraulic valve assembly responsive to a first valve signal to control hydraulic fluid flow to the first and second hydraulic cylinders, and responsive to a second valve signal to control hydraulic fluid flow to at least the third hydraulic cylinder; and   a digital control circuit coupled to the position sensors, the joystick, and the hydraulic valve assembly to apply the first and second valve signals to the valve assembly such that hydraulic fluid flow is applied to the first and second hydraulic cylinders to pivot the arms so that the first position signal and the first control signal maintain a first predetermined relationship, and hydraulic fluid flow is applied to at least the third hydraulic cylinder to pivot the bucket so that the second position signal and the second control signal maintain a second predetermined relationship, wherein the second valve signal is generated independently of the second control signal when the joystick is only moved about the first axis such that at least the third hydraulic cylinder pivots the bucket to maintain a predetermined orientation between the bucket and the frame while the arms are pivoted by the first and second hydraulic cylinders.   
     
     
       13. The control of claim 12, wherein the first and second signal generators are first and second respective potentiometers coupled to the lever such that the first potentiometer is operated in response to motion of the lever about the first axis, and the second potentiometer is operated in response to motion of the lever about the second axis. 
     
     
       14. The control of claim 13, wherein the control circuit includes an analog-to-digital converter which converts the control signals generated by the potentiometers to digital control signals. 
     
     
       15. The control of claim 12, wherein the control circuit is configured such that the predetermined orientation is a substantially constant angle between the bucket and the frame. 
     
     
       16. The control of claim 15, wherein the hydraulic valve is a pulse-width-modulated (PWM) valve, and the control circuit is configured to generate first and second valve signals which are PWM signals. 
     
     
       17. The control of claim 12, wherein the control circuit is configured to apply the first and second valve signals to the valve assembly such that hydraulic fluid flow is applied to the first and second hydraulic cylinders to pivot the arms so that the rate of change of the first position signal and the rate of change of the first control signal maintain a fourth predetermined relationship, and hydraulic fluid flow is applied to the third hydraulic cylinder to pivot the attachment so that the rate of change of the second position signal and the rate of change of the second control signal maintain a fifth predetermined relationship. 
     
     
       18. The control of claim 17, wherein the control circuit is configured such that the first, second, fourth, and fifth predetermined relationships are proportional relationships. 
     
     
       19. The control of claim 18, wherein the fourth and fifth predetermined relationships are also integral relationships. 
     
     
       20. A loading vehicle comprising: a frame;   wheels for movably supporting the frame relative to a surface supporting the vehicle;   an engine supported by the frame;   a hydraulic pump coupled to the engine;   first and second arms pivotally supported by the frame;   a bucket pivotally attached to the first and second arms;   first and second hydraulic cylinders connected between the frame and the first and second arms, respectively, to pivot the arms;   at least a third hydraulic cylinder for pivoting the bucket relative to the arms;   at least a first position sensor coupled to at least one arm and the frame to generate a first position signal representative of the position of the arms relative to the vehicle;   at least a second position sensor coupled between at least one arm and the bucket to generate a second position signal representative of the position of the bucket relative to the arms;   a joystick including a lever moveable by an operator about first and second axes, a first signal generator for generating a first control signal representative of motion of the lever about the first axis, and a second signal generator for generating a second control signal representative of motion of the lever about the second axis;   a hydraulic valve assembly responsive to a first valve signal to control hydraulic fluid flow to the first and second hydraulic cylinders, and responsive to a second valve signal to control hydraulic fluid flow to at least the third hydraulic cylinder; and   a digital control circuit coupled to the position sensors, the joystick, and the hydraulic valve assembly to apply the first and second valve signals to the valve assembly such that hydraulic fluid flow is applied to the first and second hydraulic cylinders to pivot the arms so that the first position signal and the first control signal maintain a substantially proportional first relationship, and hydraulic fluid flow is applied to at least the third hydraulic cylinder to pivot the bucket so that the second position signal and the second control signal maintain a substantially proportional second relationship, and wherein the second valve signal is generated independently of the second control signal when the joystick is only moved about the first axis such that at least the third hydraulic cylinder pivots the bucket to maintain a predetermined angle between the bucket and the frame while the arms are pivoted by the first and second hydraulic cylinders.   
     
     
       21. The vehicle of claim 20, wherein the first and second relationships are also a function of an integral of the difference between the respective first and second position signals and the first and second control signals. 
     
     
       22. The vehicle of claim 20, wherein the first and second signal generators are first and second respective potentiometers coupled to the lever such that the first potentiometer is operated in response to motion of the lever about the first axis, and the second potentiometer is operated in response to motion of the lever about the second axis. 
     
     
       23. The vehicle of claim 20, wherein the hydraulic valve is a pulse-width-modulated (PWM) valve, and the control circuit is configured to generate first and second valve signals which are PWM signals. 
     
     
       24. The vehicle of claim 20, wherein the control circuit is configured to apply the first and second valve signals to the valve assembly such that hydraulic fluid flow is applied to the first and second hydraulic cylinders to pivot the arms so that the rate of change of the first position signal and the rate of change of the first control signal maintain a predetermined fourth relationship, and hydraulic fluid flow is applied to at least the third hydraulic cylinder to pivot the attachment so that the rate of change of the second position signal and the rate of change of the second control signal maintain a predetermined fifth relationship. 
     
     
       25. The vehicle of claim 24, wherein the fourth and fifth relationships are also integral relationships.